Event-related brain potentials to attended and ignored olfactory and trigeminal stimuli.

Event-related brain potentials (ERPs) were recorded from 26 young adults, with equal numbers of male and female subjects, using attended and ignored, olfactory and trigeminal stimuli. The amplitudes and latencies of the N1, P2, and P3 components were recorded using a single-stimulus paradigm, with an inter-stimulus interval of 60 s, employing amyl acetate as the olfactory stimulus and ammonia as the trigeminal stimulus. Subjects estimated stimulus intensity in the attend condition or continued with a visual tracking task in the ignore condition. Results indicate that olfactory information is processed 30-70 ms faster than trigeminal information for the N1 and P2 potential and 100 ms faster for the P3 ERP component. N1/P2 interpeak amplitude was greater for the trigeminal than the olfactory stimuli, and greater in the attended than ignored condition. P3 amplitude was greater in the attend than ignore condition for olfactory information processing and equivalent for trigeminal information processing. These findings suggest that neuronal resource allocation is greatest for attended stimuli and that a painful stimulus demands neuronal resources even when ignored.